In conventional space vehicles, attitude determination and control (ADCS) systems may use sun sensors having one or more photodiodes. These sun sensors consume more volume than is desirable for relatively small space vehicles, such a cubesats, and are expensive, making them less than optimal for small space vehicles.
In conventional space vehicles, ADCS systems may use star trackers consisting of either a standalone camera or a camera with processing electronics. Traditional star trackers are relatively large, have high power consumption, can require significant volume for the processing electronics, and are expensive. Miniaturized versions of these sensors also tend to have significant power and volume requirements, as well as high cost. In some cases, the star tracker is a standalone camera that requires satellite resources for processing.
Reaction wheels in ADCS systems for small cubesats and other small space vehicles pose several significant design challenges. In general, a small motor must be used due to the size and power restrictions on smaller cubesats, but the reaction wheels must be relatively large and heavy to provide a sufficient moment of inertia to control the satellite. Mounting the reaction wheels directly to the motor drive shaft results in very high stresses during random vibration testing, leading to damage or destruction of the assembly. Because the wheel is spun at high rotation rates, high precision in fabrication and assembly is required. Any misalignments or wheel imbalances will typically cause the assembly to fail rapidly. Accordingly, improved ADCS systems, including sun sensors, star trackers, and reaction wheel assemblies, may be beneficial.